Statistically Fields had a terrible rookie season passing. He had more than 1 passing TD in one game only and never eclipsed 300 passing yards. That said his best receiver (Robinson) struggled through injuries and their most productive receiver was a second-year 5th round pick. Fields also had a reasonably productive season running the ball so he's got dual-threat capability. He looks very raw but has upside athleticism and could develop into a Lamar Jackson type QB (although not as good).
At this point I'd prefer Mac Jones over Fields. As another poster mentioned however I would have preferred a trade up for Micah Parsons with the next pick going after Mills or Trask. Mills was the best rookie QB in the second half of the season and Trask has good potential in the right system. Parsons was the best rookie in the NFL.
Mac Jones had a good season but like the rest of the team he struggled during the 1-4 finish. I think most people agree he needs a legit #1 receiver to go along with Bourne and Myers. Jones is in a tough spot overall when it comes to QB comparisons because there are now several exceptional young quarterbacks in the AFC… Mahomes, Allen, Jackson, Herbert, Burrow and Watson (of course depending on how his off-field issues are resolved).
Obviously Jones has just finished his rookie season and certainly he will improve but all those quarterbacks are clearly better right now. The ceilings of Mahomes, Allen, Jackson and Watson are probably out of reach. Herbert can run a little bit in addition to being a great passer. Burrow had a big jump from his rookie season with a legit WR hierarchy (Chase, Higgins & Boyd).
With McDaniels gone, I'd like to see someone with experience and proven results brought in as the OC. Joe Judge not fitting that description. Also again a clear #1 WR. That paired with a very good o-line and running game and expected improvement from Jones and the offense should be in decent shape. Then you just need a defense to contend with all those other QB's.